This invention relates generally to flow control apparatus such as is used for controlling the flow of various fluids, including gases and liquids.
U.S. Pat. No. 3,827,285 discloses a fluid flow control apparatus which makes use of a plunger-like closure assembly which is movable into and out of a cylindrical sleeve forming a part of the body and interposed between two fluid spaces or passages. The plunger establishes a seal with respect to the inner cylindrical surface of the sleeve when in closed position, by the use of cup-shaped sealing members of resilient material. The cup-shaped sealing members are faced in opposite directions. When the assembly is retracted from the sleeve and the sealing members relaxed, the annular edge portions of the rims of the sealing members have a diameter greater than the diameter of the cylindrical surface. When the assembly is moved into the sleeve, the rims of the sealing members are contracted, and have sealing engagement with the cylindrical surface.
Apparatus as described above functions satisfactorily when the flow rates and fluid pressure differentials are not great. If it is attempted to use such apparatus on surfaces where the fluid pressure differentials are relatively high, coupled with high fluid flow rates as the plunger is moved between open and closed positions, the resilient sealing members may be distorted from normal operating configurations, whereby the sealing members may suffer injury and the apparatus as a whole made inoperative or ineffective to maintain a tight shut-off.